Ink-jetting printing systems are known in the art, and thus extensive description of such devices is not required herein. Hot-melt inks typically used with ink-jet printers have a wax-based ink vehicle, e.g., a crystalline wax. Such solid ink-jet inks provide vivid color images. In typical systems, the crystalline-wax inks are jetted onto a transfer member, for example, an aluminum drum, at temperatures of approximately 130-140° C. The wax-based inks are heated to such high temperatures to decrease their viscosity for efficient and proper jetting onto the transfer member. The transfer member is at approximately 60° C., so that the wax will cool sufficiently to solidify or crystallize. As the transfer member rolls over the recording medium, e.g., paper, the image comprised of wax-based ink is pressed into the paper.
However, the use of crystalline waxes places limitations on the printing process. First, the printhead must be kept at about 130° C. during the printing process. Moreover, when the printhead is cooled and re-warmed, the resulting contraction and expansion of the ink requires a purge cycle to achieve optimum printhead performance. Furthermore, increased mechanical robustness is desired.
While such known ink compositions are used successfully, a need remains for improved phase-change ink compositions suitable for hot-melt ink-jet printing processes. There is still a need for ink compositions that can be processed at lower temperatures and with lower energy consumption, that have improved robustness, and that have improved jetting reliability and latitude with respect to meeting both the jetting and transfuse requirements of curable ink compositions. In addition, a need remains for phase-change ink compositions that exhibit desirably low viscosity values at jetting temperatures, that generate images with improved look and feel characteristics, that generate images with improved hardness and toughness characteristics, and that are suitable for high-speed printing, thereby enabling transaction and production printing applications. In addition, there remains a need for curable ink compositions for piezoelectric ink-jet printing that produce a stable image that can be transferred to a substrate without cracking and hardened upon cure.